Today, Wiggins finished his 10 miler at 17:58. (Alex posted that now he can relax, for a little while.) Wiggins was quoted as saying he may try the course again Thursday, as apparently it was quite windy, even delaying the race almost an hour.Still in great form for next month. Dowsett looked pretty fast in his time trial (not the same race) doing 26 k in 31 minutes.

Brad: “I’m not a weather man, but if you have really low pressure, under 1,000 [grams per cubic metre], you will travel a lot further on the day – anything up to one kilometre for the same power. The weather forecast for the first week in June is abnormally low pressure for London for that time of year, which is fantastic.”

Me: "grams/cubic metre" is density not pressure. Pressure is measured on Pascals (N/m^3). Brad, I hope you and your team use the correct units when setting your ride schedule.

Brad: “I’m not a weather man, but if you have really low pressure, under 1,000 [grams per cubic metre], you will travel a lot further on the day – anything up to one kilometre for the same power. The weather forecast for the first week in June is abnormally low pressure for London for that time of year, which is fantastic.”

Me: "grams/cubic metre" is density not pressure. Pressure is measured on Pascals (N/m^3). Brad, I hope you and your team use the correct units when setting your ride schedule.

Well he may not be a physicist and has his terms mixed up, but he's partly right in that barometric pressure has a direct influence on air density, which is the parameter that matters.

He is quoting air density values, although we typically report those as kg/m^3.

For the same air temperature and at the same power output, the difference in distance attainable between a low pressure 990hPa day and a high pressure 1030hPa day is approx 700 metres.

One weather site (metcheck.com) is predicting 1032mb air pressure, which doesn't look good for 55km.

Anyway, a rather basic question. How do they calculate the final distance? The only attempt I have watched was Sarah Storey's, and I expected a gun after an hour. Instead she did a final lap, which would mean they calculate the distance based on an average speed over that last lap. Is that right?

Morbius wrote:One weather site (metcheck.com) is predicting 1032mb air pressure, which doesn't look good for 55km.

Anyway, a rather basic question. How do they calculate the final distance? The only attempt I have watched was Sarah Storey's, and I expected a gun after an hour. Instead she did a final lap, which would mean they calculate the distance based on an average speed over that last lap. Is that right?

The distance = (number of complete laps x lap distance) + (lap distance x time remaining at start of incomplete lap / time taken for final completed lap)

e.g. say rider on a 250m track crossed line at 59:50 elapsed and could not complete another full lap before 60-min had expired, and their final fully complete lap was completed in 16.000 seconds and that was their 200th complete lap.

e.g. say rider on a 250m track crossed line at 59:50 elapsed and could not complete another full lap before 60-min had expired, and their final fully complete lap was completed in 16.000 seconds and that was their 200th complete lap.

Thanks Alex - as I thought, the precise distance is based on commpleted laps plus a calculation based on average speed over the last lap.

One follow up question: Do they fire a gun to indicate the last lap, and what happens if the rider is approaching the line with say 15 seconds to go, when there would be doubt over whether the lap would be the last one or whether the rider might cross the line once more before the hour is up.

The distance travelled is rounded down to the nearest metre. The record cannot be beaten by less than one metre.As a function of the average time per lap of the track by the candidate attempting the record, the timekeeper must beready to trigger the bell announcing the last lap when the time still to run is less than the average time achieved for alap of the track.The end of the attempt is announced by two pistol shots when the rider crosses the finish line after the time envisagedhas expired.If, between the expiry of the time indicating the end of the attempt and the end of the last lap, an unforeseen incident,puncture, fall, etc. does not enable the complete lap to be finished, it is the time for the previous lap that would be usedto calculate the additional distance travelled.For any record attempt, the blue-band part must be rendered unusable by means of the fitting of beading 0.50 m longand 0.08 m thick placed at the bends, every 5 metres.A record broken on the same day (by the same rider) is not ratified.A record cannot be broken by a distance of under one metre.

Morbius wrote:One follow up question: Do they fire a gun to indicate the last lap, and what happens if the rider is approaching the line with say 15 seconds to go, when there would be doubt over whether the lap would be the last one or whether the rider might cross the line once more before the hour is up.

The commissaire should only fire the gun once 60-minutes has elapsed. The bell should be rung only when it's clear a rider cannot complete another full lap although it really doesn't matter since based on the UCI's rules, the speed of the final incomplete lap doesn't matter. It's the speed of final completed lap that matters.

IOW the reality is that hour records take less than an hour to complete. It's a fun bet to guess the time a rider crosses the line on his final complete lap.